This invention relates to a liquid developer for developing electrostatic images and for use in electrophotography, electrostatic recording, electrostatic printing, etc. and to an image forming method.
Developers for electrophotography may be classified into dry developers and liquid developers. Since toners used in liquid developers have a small particle diameter of 0.1-2.0 xcexcm, liquid developers have an advantage that a clear image can be obtained. A liquid developer is generally produced by dispersing a binder resin, a colorant and a charge controlling agent in a non-aqueous solvent carrier liquid such as an aliphatic hydrocarbon.
Fixation on a transfer medium such as paper is generally carried out using a heat roller. Conventional liquid developers have problems that solvent vapors are emanated in the atmosphere during fixation, that a silicone oil should be fed for being applied to a fixation roll and that hot offset is caused during fixation.
It is an object of the present invention to provide a liquid developer which can solve the above problems.
Another object of the present invention is to provide a liquid developer which does not require a feed of a silicone oil to a fixation roll and which can prevent both generation of solvent vapors and offset during fixation.
It is a further object of the present invention to provide a liquid developer which can permit low temperature fixation.
It is a further object of the present invention to provide an image forming method which can give images with a high image density and resolution.
In accordance with one aspect of the present invention, there is provided a liquid developer comprising a carrier liquid containing silicone oil, toner particles each containing a coloring agent and a resin, and an erucamide compound.
In another aspect, the present invention provides a liquid developer comprising a carrier liquid containing silicone oil, and toner particles dispersed in said carrier liquid and each containing a coloring agent and a resin, said resin contains at least one member selected from the group consisting of the following resins (a)-(g):
(a): rosin polymers having a softening point of 50-190xc2x0 C., a glass transition point of 10-170xc2x0 C. and a molecular weight of 2,000-40,000 and obtained by reacting
(a1) a rosin glycidyl ester,
(a2) dicarboxylic acid or dicarboxylic anhydride,
(a3) at least one crosslinking agent selected from the group consisting of polyfunctional epoxy compounds, tri- or more polybasic acids or anhydrides thereof tri- or more polyhydric alcohols, and
(a4) a dihydric alcohol;
(b): vinyl polymers having a ratio of the weight average molecular weight to the number average molecular weight of greater than 4;
(c): olefin resins having a melt index of 2.5-700;
(d): polyolefins or polyolefin copolymers having an acid value of 0.5-80 and a melt viscosity of 50-20,000 mpaxc2x7s at 200xc2x0 C.;
(e): polymers obtained by crosslinking carboxyl group-containing vinyl polymers with an amine;
(f): vinyl polymers having at least 0.005% by weight of a crosslinking monomer based on a total monomer; and
(g): silicone copolymers, silicone rubber or silicone-modified resins.
The present invention also provides a liquid developer comprising a carrier liquid containing silicone oil, and toner particles dispersed in said carrier liquid and each containing a coloring agent and a resin, said toner particles having such a particle size distribution on weight basis that provides two peaks in a particle diameter range of 0.01 xcexcm or more but less than 10 xcexcm and a particle diameter range of 10 xcexcm or more but 100 xcexcm or less, with a ratio of the area of the small particle diameter side peak to the area of the greater particle diameter side peak being 50:50 to 95:5.
A The present invention further provides an image forming method comprising contacting an electrostatic latent image-bearing surface with a thin layer of a liquid developer to develop said electrostatic latent image, wherein said liquid developer is as recited in any one of the above-described.